Studies of aluminum (III) ion-selective optical sensor based on a chromogenic calix[4]arene derivative

An optical chemical sensor based on azo-calix[4]arene derivative is developed for the determination of aluminum (III) ions in aqueous solutions. The complex formation ability of azo-calix[4]arene toward metal cations such as Li(I), Cs(I), K(I), Sn(II), Pb(II), Cu(II), Eu(III), Er(III) and Al(III) is investigated by UV-vis spectroscopy. Assessments of results reveal that the azo-calix[4]arene derivative has high affinity to Al(III). The stoichiometric ratio and the association constant were determined as 1:1 and 1.24×10(4)M(-1), respectively for the complex between Al(3+) and the azo-calix[4]arene. The sensing film is fabricated by spin coating on glass plates. Under the optimized conditions, at pH 6.8, the proposed optical sensor displays a linear response to Al(3+) over 10(-7) to 10(-5)M range with response time of 12min. The optical sensor can be regenerated with HNO3 solution. In addition to its high stability and reproducibility, the sensor shows good selectivity for Al(3+) ion.